June 24, 2022: The Centers for Disease Control and Prevention has listed Fairfield, Hartford, New London, Middlesex, Tolland, and Windham Counties in Low/Green the as part of its COVID-19 Community Levels Map. Only Litchfield, Middlesex and New Haven County are listed in the Medium/Yellow category. Residents who live in the Medium /Yellow counties who are at a high risk for severe illness, should talk to their health care provider about whether to wear a mask and take other precautions. These residents should stay up to date with their COVID-19 vaccines and get tested if they have symptoms. Visit the CDC COVID-19 Community Levels Map for updates.

Mosquito-borne Diseases

Connecticut Mosquitoes


Mosquito-borne diseases are those spread by the bite of an infected mosquito. These diseases can be caused by viruses or a parasite. Viruses cause the majority of mosquito-borne diseases, and there are no medications to treat the symptoms caused by these viruses. Some mosquito species found in Connecticut are capable of spreading viruses that can cause disease in humans. Illness associated with these diseases ranges from mild to significant, and some can cause death. In Connecticut, surveillance is conducted to identify travel-related diseases (diseases acquired out of the state or out of the country) and diseases that can be spread by mosquitoes in the state. The Connecticut Department of Public Health conducts surveillance for the following mosquito-borne diseases:


California Serogroup viruses (e.g. Jamestown Canyon, LaCrosse)

Chikungunya virus



Eastern Equine Encephalitis


Saint (St.) Louis Encephalitis

West Nile virus

Yellow fever

Zika virus


The most effective way to avoid getting sick from mosquito-borne diseases is to prevent mosquito bites.


National Mosquito-borne viral disease Surveillance Summary


Connecticut Mosquito Management Program


The Connecticut Mosquito Management Program is a collaborative effort involving the Department of Energy and Environmental Protection, Connecticut Agricultural Experiment Station, Department of Public Health, Department of Agriculture, and the University of Connecticut Department of Pathobiology and Veterinary Science. The program provides information about the species of mosquitoes found in Connecticut and guidance about how to protect yourself and your community from mosquitoes and mosquito-borne diseases.

Mosquito FAQs

West Nile virus FAQs

Eastern Equine encephalitis FAQs

Repellents FAQs


Connecticut Agricultural Experiment Station


The Connecticut Agricultural Experiment Station conducts mosquito trapping across the state during June through October. Mosquitoes are tested for viruses that can cause human disease, including those found in Connecticut such as Eastern Equine Encephalitis virus, Jamestown Canyon virus, and West Nile virus 


Mosquito Trapping and Arbovirus Testing Program

Current Mosquito Testing Results

Past-Years Summaries of Mosquito Testing Results

Identification Guide to the Mosquitoes of Connecticut  

Vector-borne Disease Symposium - Symposium of Mosquito-Borne Disease in Connecticut, held on April 11, 2019.


Additional Resources


Connecticut Provider Reporting Resources

Reporting of Diseases, Emergency Illnesses, Health Conditions, and Laboratory Findings

Connecticut Provider Reporting Information

Reportable Disease Confidential Case Report form, PD-23 

Connecticut Laboratory Reporting Information

Reportable Laboratory Findings form OL-15C

Current List of Reportable Diseases


Connecticut Annual Infectious Diseases Statistics


National Resources

Workplace Safety - Mosquito-Borne Diseases - NIOSH

Vector Control Resources - CDC EHS



This page last updated 11/10/2020.